Sear mechanism for guns



Nov, 20, 1934.

c. F. HoFsTETTl-:R 1,980,994

SEAR MECHANISM FOR GUNS Filed June 17, 1932 Inventur ElarE'nEE F- HnftEtter A tnr'ney s bolt moves in recoil.

` Patented Nov. 20, 1934 .UNITED srTi-:s PAT Ar (Granted .under the actof March s, i883, as

- amendedApx-'il 30, 1928; 379 0. G. 757) l The invention describedherein may be manufactured and used by or for the. Government forgovernmental purposes, without the` payment to me ofV any royaltythereon v `This inventionV relates toa sear mechanism for guns.

' In` fixed machinegunsj mountedfon aircraft and adapted to fire betweenthe blades ofthe pro,-

peller it is customary toempl'oy a Ytrigger motor,

m synchronized with the motor-drivingthe` propeller, for actuating thesearof the gun. Y

Thefprincipal object ofthisinventionis to provide` a sear mechanism of,`the type described `whiclrmay belapplied o-existing breechboltsv 15-without requiring modification thereof, and which will be positive inaction while necessitatingthe application of only a slight force tooperate the The present invention is characterized by a 2Q novel methodof moving the sear intoengagel ment with the ring pin; of locking andunlocking thesear, r,and controlling the locking means.,

l To these -andl other; ends, the invention 4consists in theconstruction, arrangement and combination of elements describedhereinafter and pointed out in the claims specification.` j

l A ,practical enlbovzliment4 ,o fl the invention -is illustrated in the`accompanying drawing,

Fig.1 iis a. longitudinal V'sectional `vviewA through the receiver of agun and showing a part of the breech bolt insection.

Fig. 2 isa longitudinal sectional. view of [the rear end of 4the breechbolt Showingthe arrange,-

rnent. of the. parts with the firing pin in cpcked' position. Fig. 3 isa view similar to pin `in red positi on.` i

Figs. 4 and 5 are views inl rear Fig. `2 rwith menging elevation of thebolt corresponding respectively to Figs. `2 andlS.

` Fig. 6^is a View infront elevation ofthe slide:

ligs'. 7 and 8 are views respectively increar and front elevation of theSear.

Figf9is av plan-view ofl the spring for the slide.`

Referring to the drawing by numerals of reference there is shown thereceiver frame 5 of a machine gun within which a bolt 6 is reciprocallymounted. Within the bolt is a longitudinally Well `known manner bythe'lever 10 when `the forming a. partof this the searlwhen the iiringThe firing pin` is held in cocked position by means` of a sear 11 which,with only a. slight` modification, isthe` sear provided on the Browningmachine l gun, many of which are now in service. sliding movement in aslot l2 in the rear end of the bolt and is ,formed with ribs 13 on itsopposite. sides which fit in grooves 14 in the side walls of the slot.The sear includes a forwardly projecting arm 15 formed with a transverseshoulder 16 centrally on its upper face. This shoulder is adapted toengage a shoulder 17 formed by recessing or grooving the under side ofthe firing pinladjacent its rear end. The shoulders 16 and 17.. arecomplementarily inclined so that-the firing pin inf moving forward underthe influence of its vspring may., exert a camming action tot depressthe-spar. p

The` upper portion of the rear end of the firing pin is beveled toprovide a. cam surface 18 adapted to act4 on an inclined surface 19 ofthe lug 20 on the front face of the sear whereby the sear isautomatically raised during cooking of the firing pin-to bring theshoulders 16 and l'iinto engagement.

The sear is held in the raised or locking position by means of a slide21 mounted in a transverse slot 22 in the rear end of the bolt, at oneside of theslot 12` and having ribs 23 on its opposite sides working ingrooves 2,4 inthe wallsof the slot. The connection between, the searand'slide is leffected by means of a square lug 25` onthe rear vface ofvthe sear. andv the surfaces provided by a` channelr26 in the front faceofthe slide. The

channelisformed with a stepped floor, the upper J stepr27adapted toengage `the lug 25 and'hold the This sear is mounted for vertical asearin the elevated position whereby t'ol'cck the firing `pinin cockedposition and the lower step 28 adapted'to engage the lug andlimitdepression of shownnlFig. 5. l

The slide is normally maintained in the searlocl'ring position, Figs. 2and 4, by meansof `a. nat spring 29 secured tothe pin 9 and having itsextremitydisposed'iri'a; slotSO in the top rib 23. The spring moves"'theslide to the left, 'its action `being limited by the left side wall ofthe slot 12. Movement of the slide tol the right is limited byengagement of theinner end of the slide with the right hand wall of theslot 12. An offset 31 intermediate the length of the spring 29 isdisposed in a recess 32 in the bolt and serves to hold the spring inengagement with the slide as well as to prevent withdrawal of the pin 9.

pin moves forward as In Figs. 2 and 4 the shoulder 16 on the arm 15 ofthe sear is engaging the shoulder 17 of the firing pin which is incocked position and the sear is prevented from being lowered relative tothe firing pin by virtue of the engagement of its lug 25 with the upperstep 27 yin the slide ,21.v The slide is maintained in the lockingposition by the spring 29. When the slide is moved to the right the lug25 is free to be moved downwardly to the lower step 28. The sear isdepressed through the action of the firing pin, being cammed down due tothe action of the shoulders 16 and 17 when the firing pin is movedforward under the influence of its spring 8. l I

Downward movement of lthe sear is arrested when the lug 25 rests on thelower step 28. In this position the lug 25 opposes the return movementof the slide.

As the bolt moves in recoil the cocking lever 10 retracts the firing pinand compresses the firing pin spring. The cam surface 18 on the iiringpin acts on the inclined surface 19 of the lug 20 and elevates the searto the position shown in Fig. 2 with the shoulder 1'6 of the arm 15engaging the shoulder 17 of the firing pin. The lug 25 on the sear isnow in the upper part of the channel 26 in the slide and the slide isfree to be moved to the left by its spring 29 to position the upper step27 underneath the lug.

I claim:-

1. In a gun, a breech bolt, a firing pin having a beveled upper rear endand a shoulder on its under side adjacent the rear end, a firing pinspring, means for cooking the iiring pin, a vertically movable searcarried by the bolt, an arm on the lower end of the Sear having ashoulder engageable in front of the shoulder on the firing pin, a lug onthe front face of the sear engageable by the beveled rear end of thering pin to elevate the sear, a lug on the rear face of the sear, atransversely movable slide mounted in the bolt and having in its frontface a channel with a stepped floor, the lug on the sear positionable insaid channel, and a spring normally holding the slide in a positionwhere the floor of the upper step in the channel will engage the lug on'the rear face of the sear.

2. Ina gun, a breech bolt, a firing pin movable relative to the bolt, afiring'pin spring, means for cooking the firing pin, a verticallyslidable sear carried by the'bolt and engageable with the under side ofthe ring pin, a lug on the sear engageable by the rear end ofthe firingpin whereby it is cammed upwardly bythe ring pin whenthe firing pin iscocked, a lug on the rear face of the sear, a transversely movable slidemounted in the-bolt and having in its front face a channel with astepped floor, the lug'on the sear polsitionable in the channel andmeans normally holding the slide in a position where the floor of theupper step'in the channel will engage thek lug on the sear.

3. In a gun, a breech bolt, a iiring pin movable relative to the bolt, aring pin spring, means yfor cooking "the ring pin, a vertically movablesear carried by the bolt and engageable with the under side of the ringpin, means on the sear whereby it is cammed upwardly by the ring pinwhen the firing pin is cocked, a transversely movable slide in the bolt,means on the slide for holding the sear in raised position and releasingsaid sear when the slide is moved, means on the slide for limitingdownward movement of the sear and a spring for normally moving the slideinto a position where the rst mentioned means is operative.

4. In aY gun,'a breech bolt, a ring pin movable relative to the bolt, asear for holding the firing pin in retracted position, means on the searwhereby it is cammed upwardly by. the firing pin into position ofholding engagement therewith, a slide movable transversely of the sear,means on the slide for maintaining the sear in holding engagement withthe iiring pin, and means on the slide for supporting the Sear when itis out of engagement with the ring pin.

5.-'In a gun, a breech bolt, a ringpin movable relative tothe bolt andhaving a beveled upper rear end, a sear'vertically slidable in vthebreech bolt for holding the ring pin in retracted position, va lug onthe sear engageable by the beveled rear end of the firing pin whereby itis cammed upwardly by the iiring pin in position of holding engagementtherewith, and a slide movable transversely of the bolt for maintainingthe sear in holding engagement with the firing pin` 6. In a gun, abreech bolt, a nring pin movable relative to the bolt, a sear verticallyslidable in the Abreech bolt for holding the firing 'pin in retractedposition, a beveled lug on the sear engageable by the rear end of thering pin whereby 1,10

it is cammed upwardly by the ring'pin in position of holding engagementtherewith, and means for maintaining the sear in holding engagementwithv the firing pin.

7. In a gun, a bolt,-a ring pin in the bolt, a ring pin spring, a pinpassing through the bolt and'seating the firing pin spring, a lever forcocking the bolt, a sear carried by the bolt and engageable with thefiring' pin to holdv it in cocked position, a slide movable'transversely `of and engageable with the sear to hold it in engagementwith the firing pin, and a spring carried by the pin and positionedadjacent'the cooking lever, said spring acting on the slide to normallyhold it in engagementy with the sear. A

8. In a gun, a bolt having a groove, a in the bolt, ay firing pinspring, a pin passing through the bolt and seating the ring pin spring,afleverfor cooking lthe bolt, a sear carried by the 72 firing pin 1 5boltr and engageable with the firing pin to hold i it in cockedposition, aslide movable transversely of and engageable with the sear tohold it in engagement with the nring pin, and a spring Ycar-v ried bythe pin and positioned adjacent the cock'- ing lever, said spring actingon the slide to no1- -mally hold it in engagement with the sear andhavinga portion normally disposed in the groove of the bolt.

' CLARENCE F. HOFSTETTER.

